KR20030040219A - Internal fault indicator for power electrical devices - Google Patents

Abstract

An internal fault indicator for an electrical device is triggered by a sudden increase in pressure as occurs when an insulation failure creates an electric arc. The heat released in the arc is transferred onto the surrounding volume causing localized overheating, vaporization and decomposition of the insulating material. The resulting pressure surge moves a diaphragm. The movement of the diaphragm releases a spring driven plunger from a barrel which extends through the housing of the electrical device. Prior to activation the plunger is held in an "armed" position by a retaining pin. Upon triggering, the plunger is pushed by the spring until it protrudes from the housing to provide a visual signal of the internal fault. A pressure relief valve may be integrated with the internal fault indicator.

Description

INTERNAL FAULT INDICATOR FOR POWER ELECTRICAL DEVICES}

The power distribution grid uses electrical elements such as transformers, reactors, capacitors and the like. If aging or operating stresses cause failure of the insulation system, a potentially hazardous situation can arise in the above-mentioned devices. Short circuits within the device can release large amounts of energy in a very short time. In the worst case, the device may explode by a sudden increase in internal pressure due to the insulating oil vaporizing and the oil vapor decomposing into flammable or volatile gases.

Nearly all distribution poles transformers are protected by breakers that include discharge fuses or other quick acting protection devices. Such a breaker can minimize the damage by disconnecting the failed device from its power supply to block the arc current in the event of an overload or an internal fault or the like. The worker can also use the breaker as a manual switch to power or disconnect specific circuits. If the system is overloaded and the breaker is activated, the worker can easily locate the open breaker and know that the transformer disconnected by the open breaker is stopped. If there is a fault downstream of the transformer, once the fault has been repaired, it is simple for the worker to replace the fuse in the breaker and repower the circuit.

In the event of a transformer failure, closing the breaker before the transformer is repaired may cause an arc in the transformer. If power is reapplied before the internal damage caused by this arc is repaired, the failed device will surely fail again. The arc can leave a carbonized path in the device, impairing the mechanical integrity of the housing or "tank" of the device. This increases the risk of serious device failure if the device is repowered. In severe cases, the transformer may explode. This can result in property damage and serious injuries to workers and any public in the vicinity. To avoid this possibility, workers should carefully inspect and take special precautions before attempting to re-power any electrical device found to be disconnected from the current system by the protective device.

Unfortunately, internal failures can occur in the device without leaving any actual visual signal that the device has failed. If the person in charge cannot ascertain that a particular device has failed, he or she may reapply power to the device without finding that the electrical device has failed. This can cause serious failure of the electrical device as described above.

It is known that in the event of an internal arc failure of the device, the pressure spikes inside the oil-filled electrical device such as a transformer or the like. This occurs because the temperature of the arc rises significantly to the temperature at which part of the oil vaporizes. Some electrical devices are filled with an electrically insulating gas such as SF ₆ . In such gas filled devices, the arc causes a surge in gas pressure.

There is a failure indicator that can visually indicate that the device has failed. These fault indicators shorten the recovery of service, while minimizing the chance of an operator's accidental power supply to the failed device. U.S. Patent No. 5,078,078, invented by the inventor of the present invention, Cuk, discloses a device for detecting an instantaneous pressure spike in a housing of a transformer or similar device. This device fits into the opening in the casing of the transformer. The moving piston detects a surge in pressure due to an internal arc failure in the transformer. The piston is provided with one or more openings such that a gentle rise and decrease in pressure in the transformer does not significantly move the piston. When the piston has traveled a predetermined distance, the indicator attached to the piston changes its appearance and retains its indication until reset. A disadvantage of this cook apparatus is that it is not easy to identify changes in the appearance of the indicator, especially at a distance. In addition, there is no easy way to prevent malfunctions during transportation and installation.

U.S. Patent 5,623,891 discloses another apparatus for detecting a surge in pressure in the housing of a transformer. The device has a diaphragm which is affected by a surge in internal pressure in the transformer. The diaphragm supports a trigger retainer that engages the trigger on an indicator shaft mounted to rotate within the housing. The indicator is mounted on the indicator shaft under the lens which is visible from the outside of the housing. When the trigger is engaged with the trigger retainer, the biasing spring biases the indicator shaft to rotate relative to the housing. When the diaphragm moves in response to a pressure surge in the transformer, the trigger retainer is moved away to release the trigger, and the deflection spring rotates the indicator shaft and the indicator so that the warning section of the indicator is placed in the position visible through the lens.

The apparatus disclosed in US Pat. No. 5,623,891 has a number of disadvantages, such as the following.

The inner surface of the indicator lens can be soiled by fumes generated during internal failures.

The outer surface of the indicator lens can be covered and hidden by ice or snow.

-This device has no way of preventing malfunctions during transport and installation.

In general, it is necessary to mount the device on the upper surface of the transformer in a position where the lens cannot be easily seen from the ground.

-This device may malfunction due to oil splashing, etc.

If the device is to be mounted on the side of the transformer housing, there must be a space larger than the normal air space in the transformer housing, otherwise the diaphragm will be partially locked.

There is a need for an internal fault indicator for electrical equipment of the type used for power distribution that provides a clear visual indication that the device has failed and eliminates some of the drawbacks of the prior art.

The present invention relates to an indicator that signals that an internal failure has occurred in oil filled or gas filled electrical equipment such as transformers, reactors, capacitors and the like. The invention applies in particular to electrical components used in power distribution systems. Specifically, the present invention relates to an internal failure indicator that displays a visual indication when abnormal spikes in pressure are detected in the housing of the electrical device.

The accompanying drawings illustrate non-limiting embodiments of the invention.

1 is a partial cutaway view of a power transformer equipped with an internal fault indicator in accordance with the present invention and connected to a power source,

2A is a cross sectional view of an internal failure indicator in accordance with the present invention;

FIG. 2B is a cross-sectional view detailing a portion of the internal failure indicator shown in FIG. 2A with a shipping lock in place to prevent the internal failure indicator from being activated early; FIG.

2C is a cross sectional view of an internal failure indicator in accordance with a variation of the present invention wherein the coil spring is used to provide a biasing force to the trigger pin,

3 is an exploded view of the internal failure indicator shown in FIG. 2,

4 is a perspective view of the internal failure indicator shown in FIG. 2 before operation,

5 is a perspective view of the internal failure indicator shown in FIG. 2 after operation;

6 is a perspective view of an internal failure indicator having its shiping lock in place;

7A is a schematic diagram showing one possible configuration for preventing the barrel of the internal failure indicator according to the invention from rotating in an opening in the housing of the electrical device,

7b is a schematic diagram showing another possible configuration for preventing the barrel of the internal failure indicator according to the invention from rotating in the opening in the housing of the electrical device,

8 is a cross-sectional view of the internal failure indicator according to a modification of the present invention,

FIG. 9 is an exploded view of the internal fault indicator shown in FIG. 8;

FIG. 10 is a partial cutaway view of the internal failure indicator shown in FIG. 8 with some components removed for clarity of illustration. FIG.

11A and 11B are partial cutaway views illustrating in detail the locked and unlocked states of the locking mechanism of the internal failure indicator shown in FIG. 8, respectively;

12 is an isometric view of a diaphragm having a deformable structure that can be used for a failure indicator in accordance with the present invention.

The present invention provides a warning indicator for oil filled electrical equipment such as power transformers and the like. This warning indicator detects a surge in pressure generated in the housing of the electrical device due to an internal electrical failure, but does not respond to changes in pressure due to normal temperature fluctuations. In order to warn personnel not to make a potentially dangerous attempt to re-power a failed member of electrical equipment, the marking is used to clearly identify the internally failed electrical device.

Accordingly, one aspect of the present invention is to provide a failure indicator indicating that a surge in pressure has occurred in a housing of an electrical device. The failure indicator includes a barrel that can be mounted in an opening in the housing of the electrical device and an actuation mechanism. The mechanism is a chamber inside a housing, the chamber having one or more orifices that flow between an inner surface and an outer surface of the chamber; And an actuating member that can be moved in response to the pressure difference between the inner surface and the outer surface of the chamber. The failure indicator also has a plunger inside the bore of the barrel. This plunger is deflected outwardly from the barrel and is usually held by the actuating member in the actuation standby position. If the pressure difference is clear, the actuating member is moved so that the plunger can be moved outwardly in the bore to the activated position.

The chamber includes a diaphragm, and preferably, an operation member is attached to the diaphragm. This actuating member preferably includes a trigger pin that projects from the diaphragm and engages the trigger notch of the plunger when the plunger is in its operational standby position. It is preferable that both of these diaphragms and barrels are oriented almost horizontally. This miniaturizes the fault indicator.

Another aspect of the invention provides a failure indicator indicating that a surge in pressure has occurred within a housing of an electrical device. The fault indicator includes pressure surge detection means for moving the actuating member in response to a surge in pressure in the housing of the electrical apparatus; An instructing means actuated by this pressure spike detecting means, comprising: a plunger movably disposed in the bore, the plunger being directed outward from the operation standby position in the bore upon movement of the actuating member. Indicating means that can be moved; And retaining means for preventing the plunger from being separated from the failure indicator.

Another aspect of the invention provides a method for indicating that a spike in pressure has occurred within a housing of an electrical device. The method provides a plunger comprising a sealed volume and a chamber comprising an air space inside the housing and an orifice that flows between the sealed volume and inside the housing of the electrical device, the plunger having an invisible hidden cover. Steps; Applying a pressure rise in the housing to displace the wall portion of the chamber inwardly; Releasing a plunger in response to movement of said wall portion; And moving the plunger to expose the concealment portion of the plunger.

Other features and advantages of the present invention are described below.

The invention is now described using an example of an internal fault indicator for a power transformer. It will be appreciated that the present invention does not only have applications for transformers, but also applications for high power devices in general. 1 shows a conventional distribution post 10 having a timber 12 supporting a power line 14. A transformer 16 is mounted to the column 10 and connected to one of the power lines 14 through a fuse-type breaker 18. When the breaker is open, the breaker pivots down as illustrated by the dashed line in FIG. 1. This breaks the circuit between the transformer 16 and the power line 14.

Transformer 16 has a housing or "tank 20". An internal failure indicator 22 (also referred to as an internal failure detector) is mounted in the opening 24 (best seen in FIG. 7A) in the side wall of the housing 20. The opening 24 is preferably a small hole. For example, opening 24 may be a hole approximately 1 inch (25.4 mm) in diameter. The housing 20 contains an electrically insulating oil (or gas). The internal failure indicator 22 is disposed in the air space above the oil level of the housing 20.

As shown in FIG. 2A, the internal failure indicator 22 detects a momentary pressure surge in the housing 20 and changes appearance when the actuator mechanism 26 and this actuator mechanism detect a momentary pressure surge. Indicator mechanism 28. In addition, the internal failure indicator 22 preferably includes a sipping lock 30 which prevents the indicator mechanism 28 from starting at the time of installation. In addition, the internal failure indicator 22 may conveniently include an integrated pressure relief valve 32. The shiping lock 30 may prevent the pressure relief valve 32 from operating.

An electric arc is generated when the powered element of transformer 16 or the insulator surrounding the " active " element is broken. Electric arcs dissipate large amounts of energy. If energy is suddenly dissipated in the housing 20, the pressure rises rapidly in the housing 20. Even at short-circuit current levels as high as 100 amps, the pressure inside the housing 20 rises at a significantly greater rate than any other pressure rise theoretically expected to occur during normal operation of the transformer 16. This increase in pressure is detected by the actuator mechanism 26 which activates the indicator mechanism 28.

If the pressure rises to a value greater than the set value of the pressure relief valve 32, the pressure relief valve 32 is opened until the pressure is released. The pressure inside the housing 20 can rise to a level at which the pressure relief valve 32 can be opened even by normal fluctuations in ambient temperature and load. In addition, the person in charge may operate the pressure relief valve 32 manually as described later, so that the ambient pressure inside the housing 20 and the pressure outside the housing 20 are the same.

As best seen in FIGS. 2A and 3, the actuator mechanism 26 includes a chamber 40 that is open to the interior of the housing 20 only by a small orifice 42. Thin diaphragm 44, which acts as a gas barrier and is supported by compliant structure 46, forms a wall of chamber 40. In the illustrated embodiment, the compliant structure includes a helical spring 48. The helical spring 48 is preferably configured to lie on a spherical surface when in a balanced state. The diaphragm 44 has a first face 44A in the chamber 40 and a second face 44B exposed to ambient pressure inside the housing 20. The chamber 40 is preferably almost hemispherical in order to occupy a moderately small space in the housing 20. It is preferable that the diaphragm 44 has an adequately large area so that the pressure difference around the diaphragm 44 generates sufficient force to activate the indicator mechanism 28. For example, the diaphragm 44 may have a diameter of at least 3 inches. In order to maximize reliability and sensitivity, the diaphragm 44 should face downward toward the surface of the oil in the housing 20.

Since air can enter and exit the chamber 40 via the orifice 42, the air pressure inside the chamber 40 will track slow changes in the ambient pressure inside the housing 20. For example, such a change may occur when the temperature of the transformer 16 changes. On the other hand, if the pressure inside the housing 20 rises very suddenly, it will take some time for the air pressure inside the chamber 40 to rise because of the small size of the orifice 42. The diaphragm 44 is moved far enough to reliably maneuver the indicator mechanism 28 in response to a surge of pressure faster than approximately 0.5 to 1.5 psi / 5 ms, and the diaphragm 44 rises approximately slower than about 1 psi per second. It does not respond to variations in ambient pressure inside the housing 20. During the pressure spike period, the pressure on the surface 44B of the diaphragm 44 will momentarily significantly exceed the pressure on the surface 44A. The diaphragm 44 is urged toward the chamber 40. This will happen if an electrical arc occurs inside the housing 20 due to an electrical failure of the active element of the transformer 16. For example, the scattering cover 49 mitigates the effect of oil splashing on the diaphragm 44, as may occur when the housing 20 is shaken by an earthquake.

An axial guide rod 50 extending from the helical spring 48 protrudes into the orifice 42. The position of this guide rod 50 end projecting through the orifice 42 can be used to confirm that the helical spring 48 is properly disposed in the chamber 40 during assembly. Movement of the diaphragm 44 activates the indicator mechanism 28. In the illustrated embodiment, the trigger pin 54 protrudes from the face 44B of the diaphragm 44. The trigger pin 54 may be forced fit into a hub disposed at the center of the helical spring 48. Under normal operating conditions, the chamber 40 is exposed to various mechanical vibrations and shocks, including seismic vibrations. The mass of the diaphragm 44 and the helical spring 48 should be small in order to avoid malfunction due to such mechanical vibrations and to be able to operate quickly. The diaphragm 44 may comprise a thin layer of air impermeable material, such as a 5 mil polyethylene film or the like. The helical spring 48 may be made of a thin sheet of plastic that is suitably elastic.

Indicator mechanism 28 includes barrel 56. The flanged outer end 56A of the barrel 56 protrudes through the opening 24. An all-weather gasket 57 is provided between the outer end 56A and the outer surface of the housing 20. A nut 58 screwed into the threaded shoulder 56B of the barrel 56 is fastened against the inner wall surface of the housing 20 to ensure the integrity of the seal around the opening 24. Rotation of barrel 56 in opening 24 should be prevented. For example, by forming the opening 24 in the D-shape so that the opening 24 has the flat portion 59B engaging with the corresponding flat portion 59A in the shoulder 56B, the rotation of the barrel may be prevented. . 7B shows another structure that prevents rotation of the barrel 56 relative to the opening 24. In the embodiment shown in FIG. 7B, the protrusion 59D of the housing 59 engages the notch 59C in the shoulder 56B.

The barrel 56 is preferably small enough to fit in an opening approximately one inch in diameter. The barrel 56 is preferably made of a nonconductive material so that the barrel 56 does not provide a conductive passage through the wall of the housing 20. For example, the barrel may be made of fiber reinforced polypropylene containing additives that provide resistance to degradation due to the action of sunlight.

The plunger 60 is disposed in the bore 56C of the barrel 56. The plunger 60 is urged outward by the ejection spring 62 which is compressed between the inwardly projecting flange 56D at the inner end 56E of the barrel 56 and the plunger 60. The eject spring 62 is preferably housed within the cylindrical extension 60D of the plunger 60. Eject spring 62 is preferably attached to both barrel 56 and plunger 60. This can be done by providing tails 62A at both ends of the eject spring 62. Tail 62A is firmly engaged with the engagement portion of plunger 60 and barrel 56.

By engaging the trigger pin 54 with the trigger notch 64 of the plunger 60 until the internal failure indicator 22 is activated, the plunger 60 cannot be discharged from the barrel 56. Trigger pin 54 passes through chamfered guide opening 65 and into bore 56C. Helical spring 48 provides some spring force that contributes to seating trigger pin 54 on trigger notch 64. The plunger 60 preferably has a plunger type outer end 60B supported against the sealing ring 67 near the outer end of the bore 56C. As a result, the opening 24 is sealed, while the plunger 60 is held in its operating standby position in the bore 56C.

The side surface 60C of the plunger 60 is brightly colored and preferably has a color that is in high contrast with the color found around the transformer 16. Preferred colors are intense orange and light yellow. From the foregoing description, it can be understood that when the pressure rises inside the housing 20, the diaphragm 44 is displaced away from the barrel 56. This pulls trigger pin 54 out of trigger notch 64. The eject spring 62 then pushes the plunger 60 out of the bore 56 of the barrel 56. The plunger 60 is pressed sufficiently far outward at least from the bore 56C such that the rear end of the plunger 60 passes through the trigger pin 54 and the side 60C previously concealed in the bore 60C is angled. As shown in FIG. 5.

Preferably, after the plunger 60 is pushed outwards in the bore 56C, the outer end of the plunger 60 extends significantly past the outer opening of the barrel 56. This provides a very visual indication that a failure has occurred in transformer 16. After the plunger 60 is discharged, the shape of the internal failure indicator 22 is changed. In addition, after the plunger 60 is discharged, the brightly colored outer surface 60C of the plunger is exposed.

Immediately after the plunger 60 is pushed out of the barrel 56, the pressure in the chamber 40 will be equal to the ambient pressure inside the housing 20. As a result, the diaphragm 44 returns to its normal position. When the diaphragm 44 is restored to its normal position, the trigger pin 54 protrudes into the bore 56C. Thereby, the trigger pin 54 prevents the plunger 60 from being pushed back into the bore 56C. This prevents the transformer 16 from inadvertently returning to the operating state without passing the internal inspection. In general, whenever the internal fault indicator 22 is activated and not in normal operation, the electrical device must be opened and inspected before returning to the operating state.

As best shown in FIG. 3, the embodiment of the illustrated internal failure indicator 22 can be assembled by first coupling the barrel 56 to the opening 24 as described above, and then the chamber 40 is May be attached to barrel 56. In the illustrated embodiment, the combined chamber / splash guard assembly 68 has a barrel 56 receiving groove 69 on its bottom surface. The outer edge 69A of this groove 69 is elastic and can snap onto the outer surface of the barrel 56. When barrel 56 is received in groove 69, groove 69 engages barrel 56 to grip the barrel. With the chamber / splash guard assembly 68 installed in the barrel 56 (as shown in FIG. 2A), the trigger pin 54 enters into the guide opening 65 of the barrel 56.

Pressure relief valve 32 may be manufactured integrally with plunger 60. The pressure relief valve includes an axially movable valve member 70 that is biased to engage the valve seat by a low-rate spring 74. If the ambient pressure inside the housing 20 exceeds the atmospheric pressure outside the housing 20, there is a net outward force at the end of the valve member 70. If this force exceeds a force corresponding to a predetermined value, for example a pressure difference of 5 psi, the spring 74 is compressed to allow gas to escape from the housing 20. The valve member 70 protrudes past the spring retainer 76 to the vent cap 78. When the valve member 70 is moved axially outward, gas may exit the housing 20 via an exhaust gap between the vent cap 78 and the outer end 60B of the plunger 60. A ring or other gripping member 79 is attached to the outer end of the valve member 70 so that the housing 20 can be manually evacuated. By combining the internal failure indicator and the pressure relief valve in a single device, there is no need to provide two openings in the housing 20 and the space inside the housing 20 is preserved.

The outer end 56A of the barrel 56 may receive the shiping lock 30. 6 shows a failure indicator 22 with the shiping lock 30 installed. The shiping lock 30 is attached to the outer end 56A of the barrel 56, preventing the plunger 60 from moving outward in the bore 56C. This shiping lock 30 may be held in place until the transformer 16 is installed. After the transformer 16 is installed and before the transformer 16 is in operation, the ship lock lock 30 is removed.

In the illustrated embodiment, the shiping lock 30 has a pair of inward flanges 82 that engage grooves 84 (shown in FIG. 2B) at the outer end 56A of the barrel 56. Member. In the illustrated embodiment, the groove 84 is formed between the stepped flange at the end 56A of the barrel 56 and the outer surface of the housing 20. Preferably, the ship lock 30 must be broken in order to separate the ship lock from the end of the barrel 56.

Optionally, the internal failure indicator 22 includes a facility 85 for generating a control signal when activated. The facility includes one or more sets of electrical contacts that open or close when the internal fault indication 22 is activated. This electrical contact can be activated to generate a control signal, for example by the movement of the plunger 60 in the bore 56C or by the movement of the trigger pin 54. The electrical contact may be in the first position (open or closed) when the plunger 60 is in its operational standby position. When the fault indicator 22 is activated, the electrical contacts are switched to be in the second position (closed or open) when the plunger 60 is in its started position. Facility 85 may include other mechanisms, such as, for example, an optical fiber for communication of control signals to inform transmitter 86 that internal failure indicator 22 has been activated. The transmitter 86 generates a failure signal such as, for example, a radio signal in response to this control signal.

It will be appreciated that the internal fault indicator shown in the accompanying figures has many advantages over conventional fault indicators. It is possible to provide a single device that functions as both a pressure relief valve and an internal fault indicator, providing significant advantages over conventional devices. Since a single opening of the housing can be used for both the fault indicator and the pressure relief valve, the structure of the housing for the electrical device is simplified. It also provides wider tolerances for arranging parts inside the housing of electrical devices. A lot of space is required inside the housing of a typical electric device. In particular at the top of the electrical device. Both the pressure relief valve and the internal fault indicator should be in the air space at the top of the housing. Also, in a typical electrical device, power lines enter the housing through the upper air space region.

By providing the plunger 60 exiting the bore 56C when the fault indicator 22 is activated, a visual signal is obtained indicating that the device has failed, which can be seen much more clearly and clearly than previously possible. Lose. In operation, both the apparent "shape" and the color of the fault indicator change. In addition, since the failure indicator can be mounted on the side wall of the housing 20, it can be displayed in a position that is easier to see from the ground than the existing failure indicator that can be mounted only on the upper surface of the housing.

The structure of the internal failure indicator 22, which includes a sensor diaphragm and an indicator element that, in operation, moves in a direction substantially parallel to the plane of the diaphragm, can be mounted in an air space above the housing 20, and A small internal failure indicator 22 with a large enough diaphragm area is provided to provide good sensitivity to pressure surges within the housing 20.

By providing an indicator element that cannot be returned to its original position without opening the housing 20 after the internal failure indicator 22 has been activated, it can be reused before humans are properly inspected and repaired through human error. The likelihood of doing so is reduced.

The diaphragm assembly comprising a helical spring, such as the helical spring 48 shown in FIGS. 2A and 3, has the advantage of centering itself and allowing the trigger pin 54 to be easily moved axially.

The internal failure indicator 22 can be made to project very little from the housing 20. Thus, there is no surface where snow or ice is likely to adhere.

If an internal fault indicator 22 is used in the electrical device, the fault indicator should be designed and configured to have a long life and high reliability under all expected operating conditions. In addition, the components of the internal failure indicator 22 should be made of non-conductive material, if possible, so as not to disturb the distribution of the electric field in the device as much as possible.

8-11B illustrate the features of the internal failure indicator 122 in accordance with a variant of the present invention. Internal failure indicator 122 generally functions as described above. Parts of the fault indicator 122, which function similarly to those of the fault indicator 22, have been assigned reference numerals plus 100 as compared with the corresponding reference numerals used in FIGS.

The failure indicator 122 may be mounted to the housing 120 by inserting the threaded portion 156B into the housing through the opening 124 and using the nut 158 to secure the failure indicator 122 in place. Can be. As a result, the failure indicator 122 is more easily mounted than the failure indicator 22. The failure indicator 122 may be locked for transportation by having a member (not shown), such as a cotter pin or the like, enter through the holes 183A, 183B at the outer end of the barrel 156. This locking member prevents the plunger 160 from moving outward.

Another feature of the failure indicator 122 is that the pressure relief valve 132 can be separated from the plunger 160 as a unit. Pressure relief valve 132 is received in bore 161 of plunger 160. The plunger 160 has an opening 161A connected to the bore 161 on its lower side. When pressure relief valve assembly 132 is separated, bore 161 and opening 161A provide access to the interior of housing 120. This approach may be used, for example, to introduce insulating oil or other fluid into the housing 120, to sample fluid from or remove fluid from within the housing 120, or the like. If the failure indicator 122 provides such access, in other cases the ports needed to provide access to the interior of the housing 120 may be removed from the housing 120.

When the failure indicator 122 provides access to the housing 120 as described above, it is usually possible to prevent the failure indicator 122 from starting and at the same time provide a disabling mechanism used as an access port. desirable. In the illustrated embodiment, the actuation prevention mechanism includes a pin 190 protruding into the bore 156C of the barrel 156 and a hook 191 formed in the plunger 160. After removing the pressure relief valve 160, the failure indicator 122 rotates the plunger 160 within the bore 156 until the hook 191 engages with the pin 190 as shown in FIG. 11A. By doing so, starting can be prevented. If the failure indicator 122 needs to be enabled, the plunger 160 may be rotated until the hook 191 is completely released from the pin 190, as shown in FIG. 11B, and thereafter. Pressure relief valve 132 may be secured in place within bore 161. In the illustrated embodiment, the pressure relief valve 132 includes a pair of elastic arms 132A (FIG. 9), which engage the recess in the bore 161 to bore the pressure relief valve assembly 132 ( 161) held in place.

The failure indicator 122 has a diaphragm 144 that is formed to provide a plurality of annular concentric ridges 147 and includes a sheet of light hard material, such as polyester or the like. The shape of such diaphragms is known to provide good sensitivity to failure occurrence.

As will be apparent to those skilled in the art in light of the foregoing, numerous modifications and variations are possible in the practice of the invention without departing from the spirit and scope of the invention. E.g:

The single orifice 42 shown in the figure may be replaced by a plurality of smaller orifices, or may limit the rate at which the pressure inside the chamber 40 may move with variations in ambient pressure inside the housing 20. It can be replaced with other structures outside.

The shape of the orifice 42 may be annular or other shapes as illustrated in FIG. 2.

The compliant base 46 is preferably a helical spring, but need not necessarily be a helical spring.

The compliant base 46 may be integrally formed with the diaphragm 44.

In the illustrated embodiment, the trigger pin 54 prevents the plunger 60 from being reinserted into the bore 56C after the internal fault indicator 22 is activated. A separate detent or other one-way ratchet mechanism can be provided so that the internal failure indicator 22 can only be reset from within the housing 20.

The eject spring 62 is preferably attached to both the plunger 60 and the barrel 56, but a separate retainer cord may be provided to prevent the plunger 60 from fully exiting the internal failure indicator 22 during operation. Can be. Eject springs or retainer cords attach to both plunger 60 and transformer 16 to constitute a "holding means" that functions to prevent plunger 60 from being disconnected from failure indicator 22.

Several mechanical linkages can be used to release the plunger 60 in response to movement of the diaphragm 44.

For example, instead of using a compliant support member such as a helical spring 48 or a diaphragm 44 which deflects the pin 54 towards the plunger 60, a separate deflection means such as spring 80 is shown in FIG. 2C. As shown in FIG. 1, the diaphragm 44 may be used to deflect toward the plunger 60. In FIG. 2C, a thin gas barrier 44 ′ is supported by a light rigid plate 45 from which the fins 54 protrude. Coil spring 80 urges pin 54 into engagement with plunger 60.

The diaphragm 44 may take many different forms. For example, FIG. 12 shows another diaphragm 244 having a integrally formed radially extending rib 245 and comprising a sheet of light hard material.

Instead of the chamber 40 where one side is closed by the flexible diaphragm, the actuator mechanism 26 is:

A chamber closed by both a relatively high mass piston and a relatively low mass piston. These two pistons are concentric with each other and are connected to a spring having the same spring constant. The inertia of the high mass piston prevents the high mass piston from moving in response to a pressure surge. Both high and low mass pistons can be moved in response to small pressure fluctuations. The relative movement of the high mass piston and the low mass piston can be used to release the indicator mechanism 28.

The chamber 40 may comprise a bellows interior having a rigid end face joined by a flexible cylindrical wall. The relative movement of this rigid end face can activate the indicator mechanism 28 via a suitable mechanical linkage. One or more openings in the bellows will prevent the end face from moving in response to a gentle change in the ambient pressure inside the housing 20.

In an undesirable embodiment of the invention, the diaphragm 44 can be replaced with a rigid or semi-rigid movable piston that is displaced towards the chamber 40 in response to a surge in pressure inside the housing 20.

As described above, the chamber 40, one side of which is closed by the diaphragm, or any other mechanism, for example, may move inside the housing 20 by moving the wall portion of the cavity with a force sufficient to actuate the indicating means 28. A " pressure surge detection means " is constructed that responds to the surge of pressure.

The plunger 60 may have a shape different from the above-described shape, for example, when the plunger 60 is in its operation standby position, it is concealed inside the bore 56C and moved to the position in which the plunger 60 is started. And a flag, rod, plate, etc., with concealment to be revealed when exposed. The plunger 60 as described above, and any variant described herein which signals that the internal failure indicator has detected a failure, constitutes an “indicative means”.

The fastening device may be attached to the housing 20 or the device 22 in a different manner than illustrated herein. The fixing device may comprise different kinds of members that prevent the plunger 60 from accidentally moving to its triggering position before the internal failure indicator 22 is brought into operation. For example, the securing device may include a pin (not shown) entering through the opening of the plunger 60 to prevent the plunger 60 from moving longitudinally in the barrel 56 before the pin is removed. The securing device may also include, for example, a sliding, pivotal or removable member at the outer end of the plunger 60 that prevents the plunger 60 from moving outwardly in the barrel 56.

Eject spring 62 may include an extension spring arranged to pull plunger 60 outward from bore 56C in place of the illustrated compression spring.

The start prevention mechanism may comprise different mechanical structures which use the failure indicator 122 as an access port while at the same time preventing the plunger 160 from moving outward. For example, the start prevention mechanism may include a stop member that is movable between a fixed position that blocks outward movement of the plunger 160 and a release position that does not prevent movement of the plunger 160 when the failure indicator 122 is activated. Can be.

Accordingly, the scope of the present invention should be construed in accordance with the contents defined by the following claims.

Claims (30)

A failure indicator indicating the occurrence of a pressure surge in the housing of an electrical device, a) a barrel capable of being mounted in an opening in the housing of the electrical device; b) as an actuation mechanism, i) a chamber inside the housing, the chamber having one or more orifices that flow between the inner and outer surfaces of the chamber; Ii) an actuating member that can be moved in response to the pressure difference between the inner surface and the outer surface of the chamber An operating mechanism having a; c) Plungers inside the bore of the barrel, deflected outwards from the barrel, and are normally held in the operating standby position by the actuating member. Wherein when the pressure difference exceeds a practical limit, the actuating member is moved, thereby enabling the plunger to be moved outwardly in the bore to the maneuvered position. The failure indicator of claim 1, wherein the chamber comprises a diaphragm and the actuating member is connected to the diaphragm. The fault indicator of claim 2, wherein the actuating member includes a trigger pin that protrudes from the diaphragm and engages the trigger notch of the plunger when the plunger is in its operational standby position. 4. The failure indicator of claim 3, wherein the diaphragm and barrel are all oriented almost horizontally. 5. The failure indicator of claim 4, wherein the diaphragm has a first face facing the chamber and a second face downward, and the failure indicator includes a shatterproof opening with an opening covering the second face of the diaphragm. . 5. The failure indicator of claim 4, comprising a spring for urging the plunger outwardly in the bore. 7. The plunger of claim 6 wherein the spring extends into a cylindrical opening at the inner end of the plunger and, when actuated, the spring can push the plunger into a position such that the rear end of the plunger is outside of the trigger pin in the bore. Failure indicator. 7. The fault indicator of claim 6, wherein the outer surface of the plunger is brightly colored. The failure indicator of claim 1, comprising a spring for urging the plunger outwardly in the bore. 10. The failure indicator of claim 9, wherein the spring is attached to both the plunger and the barrel. The fault indicator of claim 1, comprising a pressure relief valve inside the plunger. 12. The pressure relief valve of claim 11, wherein the pressure relief valve is removably mounted to a bore of the plunger, and when the pressure relief valve is removed, the bore provides access to the interior of the housing equipped with an internal failure indicator. Fault indicator. 13. The device of claim 12, comprising a start prevention mechanism, the member protruding into the barrel and preventing the plunger from moving out of the barrel when the plunger is rotated in the barrel upon first detection. And a hook on the plunger that engages with the fault indicator. The fault indicator of claim 2, comprising a compliant structure supporting the diaphragm. 15. The failure indicator of claim 14, wherein the compliant structure comprises a helical spring. 3. The failure indicator of claim 2, wherein the diaphragm is comprised of a thin sheet of gas barrier material and the failure indicator includes a spring that urges the actuating member into engagement with the plunger. 3. The failure indicator of claim 2, wherein the diaphragm consists of a sheet of hard material formed to provide a plurality of annular concentric ridges. 15. The failure indicator of claim 14, comprising guide pins projecting axially from the central portion of the compliant structure, the guide pins projecting at least partially into the orifice. The fault indicator of claim 1, comprising a detachable lock at the outer end of the barrel, the lock preventing the plunger from moving outward in the bore. 20. The failure indicator of claim 19, wherein the lock comprises a member that is broken when removing the lock from the outer end of the bore. 20. The failure indicator of claim 19, wherein the lock comprises a member detachably mounted to an opening at an outer end of the barrel. The failure indicator of claim 1, wherein the outer end of the plunger comprises a flange, the flange sealingly engaging the sealing member on the barrel when the plunger is in its operational standby position. The fault indicator of claim 1, wherein the fault indicator includes a one-way mechanism in the bore that prevents the plunger from being pushed in the started position and restored to the operating standby position. The fault indicator of claim 1, comprising a signal transmitter coupled to emit a fault signal upon actuation of the fault indicator. The fault indicator of claim 1, comprising a set of electrical contacts, wherein the electrical contact is closed or open when the plunger is in its operational standby position and switched to open or closed when the plunger is in the activated position. . An electrical device comprising a failure indicator according to claim 1 comprising a closed housing, a chamber in the housing and a barrel protruding through the opening of the housing, and at least one active electrical element inside the housing. 27. The electrical device of claim 26 wherein the opening is in a side wall of the housing. A failure indicator indicating the occurrence of a pressure surge in the housing of an electrical device, Pressure surge detection means for moving the actuating member in response to a pressure surge in the housing of the electrical apparatus; An instructing means actuated by this pressure spike detecting means, comprising: a plunger movably disposed in the bore, the plunger moving outward in the bore to a position started from an operation standby position upon movement of the actuating member. Indicating means which can be moved; Retaining means for preventing the plunger from disconnecting from the fault indicator Failure indicator that includes. A method of indicating the occurrence of a pressure surge in a housing of an electrical device, a) providing a plunger having a chamber inside the housing of the electrical device, the chamber comprising an enclosed volume and an orifice for distributing between the air space inside the housing and the enclosed volume, and having a concealed hidden cover Wow; b) displacing the wall portion of the chamber inwardly by applying a pressure rise in the housing; c) releasing a plunger in response to movement of said wall portion; d) moving the plunger to expose the concealment of the plunger Display method comprising a. 30. The method of claim 29, wherein moving the plunger comprises pushing the plunger out of the bore of the housing, wherein the concealment of the plunger is a side of the plunger.